ANALYSIS - Lumpfish are being increasingly used on salmon farms to control sea lice. However the amount of sea lice eaten by lumpfish varies. Could this be related to personality? Lucy Towers, The Fish Site's Editor, reports.

Prey selection is known to be related to personality and behavioural traits. With this in mind, Asa Johannesen from the Nesvík Marine Centre, Fiskaaling, Faroe Islands, has investigated whether the behavioural differences in lumpfish relate to how they eat sea lice.

Presenting her work at Aquaculture Europe, held on 20-23 September, in Edinburgh, Scotland, Ms Johannesen explained that the different personality traits were investigated in 200 immature lumpfish, bred from wild females and reared males.

The study involved a baseline test of general activity and then video recordings being taken to observe the behaviour of fish when exposed to three items:

A novel object lowered into the tank

A quick chase with a small net (predator response)

A mirror inserted into the tank

After each of these three tests, the fish were then released into tanks with sea lice to see their eating behaviour.

The eating behaviour was determined through PCR analysis of the stomach contents, extracted from the lumpfish using a neo-natal feeding tube whilst under anaeshetic.

Although Ms Johannesen's study involved 200 fish, the results for 50 were presented (150 still left to analyse).

The behaviour tests showed that there is correlation between a variety of activity measures.

More active fish were more likely to respond to stimuli with escape or approach behaviours. Ms Johannesen explained that a small amount of fish investigated the mirror and novel object. These fish were also the most active fish.

Fish who investigated the novel object also were the ones who reacted more to the net and to the mirror, often interacting by biting or nudging the mirror.

Less active fish were more likely to remain inactive after a brief escape response to stimuli, said Ms Johannesen.

From these observations, two major behavioural types of lumpfish arose: active and inactive. Active fish are more likely to react with swimming or escape behaviours when exposed to a stimulus and inactive fish are more likely to be non-reactive when exposed to a stimulus.

In terms of which fish ate more sea lice, the more active fish during the 3 behaviour tests tended to eat the most.

This could however be more due to a lumpfish's activity level rather than its personality trait.

The link between behaviour and sea lice consumption therefore looks rather tenuous, said Ms Johannesen.

It is vital that fish farm operatives who are responsible for farmed fish are trained in their health and
welfare. This will help to ensure that fish are free from disease and suffering whilst at the same time
promote good productivity and comply with legislation.